Table of Contents
July 1997

Discover Magazine's mission is to enable readers to lead richer lives by explaining and expanding their universe. Each month we bring you in depth information and analysis from various topics ranging from technology and space to the living world we live in.

No one knows why a puzzling growth sometimes chokes off the blood vessels that embrace the heart, or who is most susceptible to it. But a seemingly harmless--and nearly ubiquitous--virus may provide a valuable clue.

Everybody has one--even rats and pigeons, to say nothing of people. The ability to grasp small numbers and map them onto a number line in the brain is an evolutionary birthright of ours. Arithmetic, of course, is another matter.